/**
 * @file
 * SLIP Interface
 *
 */

/*
 * Copyright (c) 2001-2004 Swedish Institute of Computer Science.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the Institute nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * This file is built upon the file: src/arch/rtxc/netif/sioslip.c
 *
 * Author: Magnus Ivarsson <magnus.ivarsson(at)volvo.com>
 *         Simon Goldschmidt
 */

/**
 * @defgroup slipif SLIP
 * @ingroup netifs
 *
 * This is an arch independent SLIP netif. The specific serial hooks must be
 * provided by another file. They are sio_open, sio_read/sio_tryread and sio_send
 *
 * Usage: This netif can be used in three ways:\n
 *        1) For NO_SYS==0, an RX thread can be used which blocks on sio_read()
 *           until data is received.\n
 *        2) In your main loop, call slipif_poll() to check for new RX bytes,
 *           completed packets are fed into netif->input().\n
 *        3) Call slipif_received_byte[s]() from your serial RX ISR and
 *           slipif_process_rxqueue() from your main loop. ISR level decodes
 *           packets and puts completed packets on a queue which is fed into
 *           the stack from the main loop (needs SYS_LIGHTWEIGHT_PROT for
 *           pbuf_alloc to work on ISR level!).
 *
 */

#include "netif/slipif.h"
#include "lwip/opt.h"

#include "lwip/def.h"
#include "lwip/pbuf.h"
#include "lwip/stats.h"
#include "lwip/snmp.h"
#include "lwip/sys.h"
#include "lwip/sio.h"

#define SLIP_END     0xC0 /* 0300: start and end of every packet */
#define SLIP_ESC     0xDB /* 0333: escape start (one byte escaped data follows) */
#define SLIP_ESC_END 0xDC /* 0334: following escape: original byte is 0xC0 (END) */
#define SLIP_ESC_ESC 0xDD /* 0335: following escape: original byte is 0xDB (ESC) */

/** Maximum packet size that is received by this netif */
#ifndef SLIP_MAX_SIZE
#define SLIP_MAX_SIZE 1500
#endif

/** Define this to the interface speed for SNMP
 * (sio_fd is the sio_fd_t returned by sio_open).
 * The default value of zero means 'unknown'.
 */
#ifndef SLIP_SIO_SPEED
#define SLIP_SIO_SPEED(sio_fd) 0
#endif

enum slipif_recv_state {
    SLIP_RECV_NORMAL,
    SLIP_RECV_ESCAPE
};

struct slipif_priv {
    sio_fd_t sd;
    /* q is the whole pbuf chain for a packet, p is the current pbuf in the chain */
    struct pbuf *p, *q;
    u8_t state;
    u16_t i, recved;
#if SLIP_RX_FROM_ISR
    struct pbuf *rxpackets;
#endif
};

/**
 * Send a pbuf doing the necessary SLIP encapsulation
 *
 * Uses the serial layer's sio_send()
 *
 * @param netif the lwip network interface structure for this slipif
 * @param p the pbuf chain packet to send
 * @return always returns ERR_OK since the serial layer does not provide return values
 */
static err_t slipif_output(struct netif *netif, struct pbuf *p)
{
    struct slipif_priv *priv;
    struct pbuf *q;
    u16_t i;
    u8_t c;

    LWIP_ASSERT("netif != NULL", (netif != NULL));
    LWIP_ASSERT("netif->state != NULL", (netif->state != NULL));
    LWIP_ASSERT("p != NULL", (p != NULL));

    LWIP_DEBUGF(SLIP_DEBUG, ("slipif_output: sending %" U16_F " bytes\n", p->tot_len));
    priv = (struct slipif_priv *)netif->state;

    /* Send pbuf out on the serial I/O device. */
    /* Start with packet delimiter. */
    sio_send(SLIP_END, priv->sd);

    for (q = p; q != NULL; q = q->next) {
        for (i = 0; i < q->len; i++) {
            c = ((u8_t *)q->payload)[i];

            switch (c) {
                case SLIP_END:
                    /* need to escape this byte (0xC0 -> 0xDB, 0xDC) */
                    sio_send(SLIP_ESC, priv->sd);
                    sio_send(SLIP_ESC_END, priv->sd);
                    break;

                case SLIP_ESC:
                    /* need to escape this byte (0xDB -> 0xDB, 0xDD) */
                    sio_send(SLIP_ESC, priv->sd);
                    sio_send(SLIP_ESC_ESC, priv->sd);
                    break;

                default:
                    /* normal byte - no need for escaping */
                    sio_send(c, priv->sd);
                    break;
            }
        }
    }

    /* End with packet delimiter. */
    sio_send(SLIP_END, priv->sd);
    return ERR_OK;
}

#if LWIP_IPV4
/**
 * Send a pbuf doing the necessary SLIP encapsulation
 *
 * Uses the serial layer's sio_send()
 *
 * @param netif the lwip network interface structure for this slipif
 * @param p the pbuf chain packet to send
 * @param ipaddr the ip address to send the packet to (not used for slipif)
 * @return always returns ERR_OK since the serial layer does not provide return values
 */
static err_t slipif_output_v4(struct netif *netif, struct pbuf *p, const ip4_addr_t *ipaddr)
{
    LWIP_UNUSED_ARG(ipaddr);
    return slipif_output(netif, p);
}
#endif /* LWIP_IPV4 */

#if LWIP_IPV6
/**
 * Send a pbuf doing the necessary SLIP encapsulation
 *
 * Uses the serial layer's sio_send()
 *
 * @param netif the lwip network interface structure for this slipif
 * @param p the pbuf chain packet to send
 * @param ipaddr the ip address to send the packet to (not used for slipif)
 * @return always returns ERR_OK since the serial layer does not provide return values
 */
static err_t slipif_output_v6(struct netif *netif, struct pbuf *p, const ip6_addr_t *ipaddr)
{
    LWIP_UNUSED_ARG(ipaddr);
    return slipif_output(netif, p);
}
#endif /* LWIP_IPV6 */

/**
 * Handle the incoming SLIP stream character by character
 *
 * @param netif the lwip network interface structure for this slipif
 * @param c received character (multiple calls to this function will
 *        return a complete packet, NULL is returned before - used for polling)
 * @return The IP packet when SLIP_END is received
 */
static struct pbuf *slipif_rxbyte(struct netif *netif, u8_t c)
{
    struct slipif_priv *priv;
    struct pbuf *t;

    LWIP_ASSERT("netif != NULL", (netif != NULL));
    LWIP_ASSERT("netif->state != NULL", (netif->state != NULL));

    priv = (struct slipif_priv *)netif->state;

    switch (priv->state) {
        case SLIP_RECV_NORMAL:
            switch (c) {
                case SLIP_END:
                    if (priv->recved > 0) {
                        /* Received whole packet. */
                        /* Trim the pbuf to the size of the received packet. */
                        pbuf_realloc(priv->q, priv->recved);

                        LINK_STATS_INC(link.recv);

                        LWIP_DEBUGF(SLIP_DEBUG, ("slipif: Got packet (%" U16_F " bytes)\n", priv->recved));
                        t = priv->q;
                        priv->p = priv->q = NULL;
                        priv->i = priv->recved = 0;
                        return t;
                    }

                    return NULL;

                case SLIP_ESC:
                    priv->state = SLIP_RECV_ESCAPE;
                    return NULL;

                default:
                    break;
            } /* end switch (c) */

            break;

        case SLIP_RECV_ESCAPE:

            /* un-escape END or ESC bytes, leave other bytes
               (although that would be a protocol error) */
            switch (c) {
                case SLIP_ESC_END:
                    c = SLIP_END;
                    break;

                case SLIP_ESC_ESC:
                    c = SLIP_ESC;
                    break;

                default:
                    break;
            }

            priv->state = SLIP_RECV_NORMAL;
            break;

        default:
            break;
    } /* end switch (priv->state) */

    /* byte received, packet not yet completely received */
    if (priv->p == NULL) {
        /* allocate a new pbuf */
        LWIP_DEBUGF(SLIP_DEBUG, ("slipif_input: alloc\n"));
        priv->p = pbuf_alloc(PBUF_LINK, (PBUF_POOL_BUFSIZE - PBUF_LINK_HLEN - PBUF_LINK_ENCAPSULATION_HLEN), PBUF_POOL);

        if (priv->p == NULL) {
            LINK_STATS_INC(link.drop);
            LWIP_DEBUGF(SLIP_DEBUG, ("slipif_input: no new pbuf! (DROP)\n"));
            /* don't process any further since we got no pbuf to receive to */
            return NULL;
        }

        if (priv->q != NULL) {
            /* 'chain' the pbuf to the existing chain */
            pbuf_cat(priv->q, priv->p);
        } else {
            /* p is the first pbuf in the chain */
            priv->q = priv->p;
        }
    }

    /* this automatically drops bytes if > SLIP_MAX_SIZE */
    if ((priv->p != NULL) && (priv->recved <= SLIP_MAX_SIZE)) {
        ((u8_t *)priv->p->payload)[priv->i] = c;
        priv->recved++;
        priv->i++;

        if (priv->i >= priv->p->len) {
            /* on to the next pbuf */
            priv->i = 0;

            if (priv->p->next != NULL && priv->p->next->len > 0) {
                /* p is a chain, on to the next in the chain */
                priv->p = priv->p->next;
            } else {
                /* p is a single pbuf, set it to NULL so next time a new
                 * pbuf is allocated */
                priv->p = NULL;
            }
        }
    }

    return NULL;
}

/** Like slipif_rxbyte, but passes completed packets to netif->input
 *
 * @param netif The lwip network interface structure for this slipif
 * @param c received character
 */
static void slipif_rxbyte_input(struct netif *netif, u8_t c)
{
    struct pbuf *p;
    p = slipif_rxbyte(netif, c);

    if (p != NULL) {
        if (netif->input(p, netif) != ERR_OK) {
            pbuf_free(p);
        }
    }
}

#if SLIP_USE_RX_THREAD
/**
 * The SLIP input thread.
 *
 * Feed the IP layer with incoming packets
 *
 * @param nf the lwip network interface structure for this slipif
 */
static void slipif_loop_thread(void *nf)
{
    u8_t c;
    struct netif *netif = (struct netif *)nf;
    struct slipif_priv *priv = (struct slipif_priv *)netif->state;

    while (1) {
        if (sio_read(priv->sd, &c, 1) > 0) {
            slipif_rxbyte_input(netif, c);
        }
    }
}
#endif /* SLIP_USE_RX_THREAD */

/**
 * @ingroup slipif
 * SLIP netif initialization
 *
 * Call the arch specific sio_open and remember
 * the opened device in the state field of the netif.
 *
 * @param netif the lwip network interface structure for this slipif
 * @return ERR_OK if serial line could be opened,
 *         ERR_MEM if no memory could be allocated,
 *         ERR_IF is serial line couldn't be opened
 *
 * @note If netif->state is interpreted as an u8_t serial port number.
 *
 */
err_t slipif_init(struct netif *netif)
{
    struct slipif_priv *priv;
    u8_t sio_num;

    LWIP_ASSERT("slipif needs an input callback", netif->input != NULL);

    /* netif->state contains serial port number */
    sio_num = LWIP_PTR_NUMERIC_CAST(u8_t, netif->state);

    LWIP_DEBUGF(SLIP_DEBUG, ("slipif_init: netif->num=%" U16_F "\n", (u16_t)sio_num));

    /* Allocate private data */
    priv = (struct slipif_priv *)mem_malloc(sizeof(struct slipif_priv));

    if (!priv) {
        return ERR_MEM;
    }

    netif->name[0] = 's';
    netif->name[1] = 'l';
#if LWIP_IPV4
    netif->output = slipif_output_v4;
#endif /* LWIP_IPV4 */
#if LWIP_IPV6
    netif->output_ip6 = slipif_output_v6;
#endif /* LWIP_IPV6 */
    netif->mtu = SLIP_MAX_SIZE;

    /* Try to open the serial port. */
    priv->sd = sio_open(sio_num);

    if (!priv->sd) {
        /* Opening the serial port failed. */
        mem_free(priv);
        return ERR_IF;
    }

    /* Initialize private data */
    priv->p = NULL;
    priv->q = NULL;
    priv->state = SLIP_RECV_NORMAL;
    priv->i = 0;
    priv->recved = 0;
#if SLIP_RX_FROM_ISR
    priv->rxpackets = NULL;
#endif

    netif->state = priv;

    /* initialize the snmp variables and counters inside the struct netif */
    MIB2_INIT_NETIF(netif, snmp_ifType_slip, SLIP_SIO_SPEED(priv->sd));

#if SLIP_USE_RX_THREAD
    /* Create a thread to poll the serial line. */
    sys_thread_new(SLIPIF_THREAD_NAME, slipif_loop_thread, netif,
                   SLIPIF_THREAD_STACKSIZE, SLIPIF_THREAD_PRIO);
#endif /* SLIP_USE_RX_THREAD */
    return ERR_OK;
}

/**
 * @ingroup slipif
 * Polls the serial device and feeds the IP layer with incoming packets.
 *
 * @param netif The lwip network interface structure for this slipif
 */
void slipif_poll(struct netif *netif)
{
    u8_t c;
    struct slipif_priv *priv;

    LWIP_ASSERT("netif != NULL", (netif != NULL));
    LWIP_ASSERT("netif->state != NULL", (netif->state != NULL));

    priv = (struct slipif_priv *)netif->state;

    while (sio_tryread(priv->sd, &c, 1) > 0) {
        slipif_rxbyte_input(netif, c);
    }
}

#if SLIP_RX_FROM_ISR
/**
 * @ingroup slipif
 * Feeds the IP layer with incoming packets that were receive
 *
 * @param netif The lwip network interface structure for this slipif
 */
void slipif_process_rxqueue(struct netif *netif)
{
    struct slipif_priv *priv;
    SYS_ARCH_DECL_PROTECT(old_level);

    LWIP_ASSERT("netif != NULL", (netif != NULL));
    LWIP_ASSERT("netif->state != NULL", (netif->state != NULL));

    priv = (struct slipif_priv *)netif->state;

    SYS_ARCH_PROTECT(old_level);

    while (priv->rxpackets != NULL) {
        struct pbuf *p = priv->rxpackets;
#if SLIP_RX_QUEUE
        /* dequeue packet */
        struct pbuf *q = p;

        while ((q->len != q->tot_len) && (q->next != NULL)) {
            q = q->next;
        }

        priv->rxpackets = q->next;
        q->next = NULL;
#else /* SLIP_RX_QUEUE */
        priv->rxpackets = NULL;
#endif /* SLIP_RX_QUEUE */
        SYS_ARCH_UNPROTECT(old_level);

        if (netif->input(p, netif) != ERR_OK) {
            pbuf_free(p);
        }

        SYS_ARCH_PROTECT(old_level);
    }

    SYS_ARCH_UNPROTECT(old_level);
}

/** Like slipif_rxbyte, but queues completed packets.
 *
 * @param netif The lwip network interface structure for this slipif
 * @param data Received serial byte
 */
static void slipif_rxbyte_enqueue(struct netif *netif, u8_t data)
{
    struct pbuf *p;
    struct slipif_priv *priv = (struct slipif_priv *)netif->state;
    SYS_ARCH_DECL_PROTECT(old_level);

    p = slipif_rxbyte(netif, data);

    if (p != NULL) {
        SYS_ARCH_PROTECT(old_level);

        if (priv->rxpackets != NULL) {
#if SLIP_RX_QUEUE
            /* queue multiple pbufs */
            struct pbuf *q = p;

            while (q->next != NULL) {
                q = q->next;
            }

            q->next = p;
        } else {
#else /* SLIP_RX_QUEUE */
            pbuf_free(priv->rxpackets);
        }

        {
#endif /* SLIP_RX_QUEUE */
            priv->rxpackets = p;
        }

        SYS_ARCH_UNPROTECT(old_level);
    }
}

/**
 * @ingroup slipif
 * Process a received byte, completed packets are put on a queue that is
 * fed into IP through slipif_process_rxqueue().
 *
 * This function can be called from ISR if SYS_LIGHTWEIGHT_PROT is enabled.
 *
 * @param netif The lwip network interface structure for this slipif
 * @param data received character
 */
void slipif_received_byte(struct netif *netif, u8_t data)
{
    LWIP_ASSERT("netif != NULL", (netif != NULL));
    LWIP_ASSERT("netif->state != NULL", (netif->state != NULL));
    slipif_rxbyte_enqueue(netif, data);
}

/**
 * @ingroup slipif
 * Process multiple received byte, completed packets are put on a queue that is
 * fed into IP through slipif_process_rxqueue().
 *
 * This function can be called from ISR if SYS_LIGHTWEIGHT_PROT is enabled.
 *
 * @param netif The lwip network interface structure for this slipif
 * @param data received character
 * @param len Number of received characters
 */
void slipif_received_bytes(struct netif *netif, u8_t *data, u8_t len)
{
    u8_t i;
    u8_t *rxdata = data;
    LWIP_ASSERT("netif != NULL", (netif != NULL));
    LWIP_ASSERT("netif->state != NULL", (netif->state != NULL));

    for (i = 0; i < len; i++, rxdata++) {
        slipif_rxbyte_enqueue(netif, *rxdata);
    }
}
#endif /* SLIP_RX_FROM_ISR */
